drm/nouveau: add support for MSI

Only supported on NV50+ so far, and disabled by default currently.  The
module parameter "msi=1" will enable it.

There's a kernel bug which will cause this to fail if the module (or the
NVIDIA binary driver) has ever been loaded before loading nouveau with
MSI enabled.  As such, this is only safe to enable if you have nouveau
load on boot, and don't wish to ever reload it.

The workaround is to "echo 0 > /sys/bus/pci/devices/<device>/enable"
until the enable count reads 0.  Then you should be able to load nouveau
with MSI enabled.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_irq.c b/drivers/gpu/drm/nouveau/nouveau_irq.c
index ca9b969f4f9c..17e2fa86cde7 100644
--- a/drivers/gpu/drm/nouveau/nouveau_irq.c
+++ b/drivers/gpu/drm/nouveau/nouveau_irq.c
@@ -68,8 +68,13 @@ nouveau_irq_preinstall(struct drm_device *dev)
 int
 nouveau_irq_postinstall(struct drm_device *dev)
 {
+        struct drm_nouveau_private *dev_priv = dev->dev_private;
+
         /* Master enable */
         nv_wr32(dev, NV03_PMC_INTR_EN_0, NV_PMC_INTR_EN_0_MASTER_ENABLE);
+        if (dev_priv->msi_enabled)
+                nv_wr08(dev, 0x00088068, 0xff);
+
         return 0;
 }
 
@@ -1263,5 +1268,35 @@ nouveau_irq_handler(DRM_IRQ_ARGS)
 
         spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
 
+        if (dev_priv->msi_enabled)
+                nv_wr08(dev, 0x00088068, 0xff);
+
         return IRQ_HANDLED;
 }
+
+int
+nouveau_irq_init(struct drm_device *dev)
+{
+        struct drm_nouveau_private *dev_priv = dev->dev_private;
+        int ret;
+
+        if (nouveau_msi != 0 && dev_priv->card_type >= NV_50) {
+                ret = pci_enable_msi(dev->pdev);
+                if (ret == 0) {
+                        NV_INFO(dev, "enabled MSI\n");
+                        dev_priv->msi_enabled = true;
+                }
+        }
+
+        return drm_irq_install(dev);
+}
+
+void
+nouveau_irq_fini(struct drm_device *dev)
+{
+        struct drm_nouveau_private *dev_priv = dev->dev_private;
+
+        drm_irq_uninstall(dev);
+        if (dev_priv->msi_enabled)
+                pci_disable_msi(dev->pdev);
+}